Disappointed customer with panel beater

I took my car in to XLNT panel beaters after they phoned me and told me that the part had arrived. I drove there to book the car in. That was on the 16 April 2018. On the 26th April I called again, because I had been calling the whole time to find out whether my car was ready. They told me that they were waiting for the mirror from the supplier. I mean when they said that the parts had arrived, did that not mean all the parts? Is the mirror not a part? Now, today, the 30th April when I call to inquire, they tell me about a backlog from their suppliers. They tell that the mirror will arrive in 21 day. How am I suppose to go to work, do my family responsibilities if my car will be sitting in their bay waiting for a mirror, that should have been ordered before calling me and telling me to take the car in?